Microsoft is discontinuing Windows Live Messenger in 1st quarter 2013, forcing users to switch to Skype. Most would want to switch to Skype anyway with its more advanced capabilities, and the switch makes sense to Microsoft, since they purchased Skype for $8.5 billion last year. However, the move may be seen as typical Redmondian high-handedness by those using Messenger with dial-up. Technically Skype works with dial-up but in practice most agree you really need broadband for decent use. Will everyone view Messenger as replaceable by Skype?

I think XMPP should handle all those tasks which you listed. What exactly do you think doesn't work?

For example the "no need to configure servers" - part. Average Jane or Joe does NOT want to do such and that is actually a big reason for why I have been unable to convert the people I know of to some free alternative. At most they accept having to put in a password and username, nothing else.